A First-Principles Comparative Study on the Elastic and Related Properties of Ti3AC2 (A = Si, Ir, and Au) MAX Phases

The elastic, mechanical, acoustic, and thermal properties of Ti3SiC2, Ti3IrC2, and Ti3AuC2 MAX phases were systematically investigated using first-principles calculations based on density functional theory. The computed lattice parameters and elastic, mechanical, and acoustic properties were consistent with existing experimental and theoretical findings, confirming the intrinsic mechanical stability of these MAX phases. Single-crystal elastic stiffness constants were used to derive polycrystalline elastic moduli, directional dependencies of bulk, shear, and Young's moduli, and anisotropic factors. The results revealed a ductility sequence of Ti3SiC2 < Ti3IrC2 < Ti3AuC2, with Ti3IrC2 and Ti3AuC2 exhibiting greater elastic anisotropy than Ti3SiC2. Additionally, sound velocities, Debye temperatures, minimum thermal conductivities, melting points, and Grüneisen parameters were determined. The findings showed that Ti3SiC2 outperforms Ti3IrC2 and Ti3AuC2 in sound velocity, average sound velocity, Debye temperature, and minimum thermal conductivity, while Ti3IrC2 has the highest melting point and Ti3AuC2 the largest Grüneisen parameter. These results provide valuable insights into the design of related materials for high-performance applications.